A perplexing problem faced in the commercial production of nuts and certain seeds is the separation of the shell or husk from the sought after meat. A good example is the English walnut. Handcracking of the nutshell and separation of the meat was the traditional and remains the most efficient means in terms of separating the nutmeat, which represents 42 to 44 percent of the total weight of the nut, from the nutshell. However, for large scale producers, hand cracking and separation is not suitable from a time and cost of labor standpoint.
Accordingly, mass cracking and separation methods and apparatus have been developed. One known method for separating meats from the shells is disclosed in U.S. Pat. No. 2,237,442, issued April 8, 1941 to MacFarlane entitled "Method of Shelling Nuts". By this method, whole nuts are loaded into a trommel where they are immersed in and covered by a substance such as a copper-bronze powder with pyroxylin base vehicle and acetone thinner. A portion of the trommel is perforated so that excess substance can be collected. The nuts are then dried in a tower and sent to a cracking machine. The cracked nutshells and meat aggregate leaving the cracking machine is fed into a floatation tank wherein the shells sink to the bottom and the meats float to the top. The separated shells and meats are then collected and the shells are sent for recovery of the substance.
One drawback of this type of separation method is that the trommel applies a non-uniform, non-optimum coating on the nuts. Accordingly, more than the required amount of substance is used adding to the cost of supplying and recovery of the substance. Furthermore, an overly thick, non-uniform covering tends to cause the nuts to agglomerate into an unmanageable mass which is difficult to dry and process. A thick coating is also subject to breaking or flaking away from the nut shell when the nut is cracked. Another associated problem is that process equipment must be dedicated to drying the overly coated nuts which again translates into processing costs.
Regarding recovery, often the discarded nutshells are used as filler, fuel, cosmetics or the like and accordingly the substance, which is toxic, must be removed. As can be appreciated, an overly abundant covering complicates and adds to the expense of the recovery step.
Another drawback of the above described method is the wetting of the nutshells during the separation by floatation. Should some meats be retained in the shell, additional cracking requires an intermediate drying step, again complicating the process and adding to the cost of separation.
A further disadvantage of this method is that, in the floatation tank, the nutmeats are wetted by the liquid in the tank. The coated shell pieces are also in this liquid which can have the shell coating dissolved therein, thus leading to contamination of the meats. Also, because the meats are wetted in the tank, they must be dried pursuant to a further step in the method.